[ARM] VMOVN undef folding

If we insert undef using a VMOVN, we can just use the original value in
three out of the four possible combinations. Using VMOVT into a undef
vector will still require the lanes to be moved, but otherwise the
non-undef value can be used.

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 4fca4f5..7225f66 100644 (file)
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -15424,6 +15424,14 @@ static SDValue PerformVMOVNCombine(SDNode *N,
   SDValue Op1 = N->getOperand(1);
   unsigned IsTop = N->getConstantOperandVal(2);
 
+  // VMOVNT a undef -> a
+  // VMOVNB a undef -> a
+  // VMOVNB undef a -> a
+  if (Op1->isUndef())
+    return Op0;
+  if (Op0->isUndef() && !IsTop)
+    return Op1;
+
   // VMOVNt(c, VQMOVNb(a, b)) => VQMOVNt(c, b)
   // VMOVNb(c, VQMOVNb(a, b)) => VQMOVNb(c, b)
   if ((Op1->getOpcode() == ARMISD::VQMOVNs ||

diff --git a/llvm/test/CodeGen/Thumb2/mve-vmovn.ll b/llvm/test/CodeGen/Thumb2/mve-vmovn.ll
index bfc9db2..a2b7fad 100644 (file)
--- a/llvm/test/CodeGen/Thumb2/mve-vmovn.ll
+++ b/llvm/test/CodeGen/Thumb2/mve-vmovn.ll
@@ -801,3 +801,144 @@ entry:
   %out = shufflevector <16 x i8> %src1, <16 x i8> undef, <16 x i32> <i32 0, i32 0, i32 2, i32 2, i32 4, i32 4, i32 6, i32 6, i32 8, i32 8, i32 10, i32 10, i32 12, i32 12, i32 14, i32 14>
   ret <16 x i8> %out
 }
+
+
+define arm_aapcs_vfpcc <8 x i16> @vmovn32trunct_undef2(<8 x i16> %a) {
+; CHECK-LABEL: vmovn32trunct_undef2:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    bx lr
+;
+; CHECKBE-LABEL: vmovn32trunct_undef2:
+; CHECKBE:       @ %bb.0: @ %entry
+; CHECKBE-NEXT:    bx lr
+entry:
+  %c1 = call <4 x i32> @llvm.arm.mve.vreinterpretq.v4i32.v8i16(<8 x i16> %a)
+  %c2 = call <4 x i32> @llvm.arm.mve.vreinterpretq.v4i32.v8i16(<8 x i16> undef)
+  %strided.vec = shufflevector <4 x i32> %c1, <4 x i32> %c2, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
+  %out = trunc <8 x i32> %strided.vec to <8 x i16>
+  ret <8 x i16> %out
+}
+
+define arm_aapcs_vfpcc <8 x i16> @vmovn32trunct_undef1(<8 x i16> %a) {
+; CHECK-LABEL: vmovn32trunct_undef1:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    vmovnt.i32 q0, q0
+; CHECK-NEXT:    bx lr
+;
+; CHECKBE-LABEL: vmovn32trunct_undef1:
+; CHECKBE:       @ %bb.0: @ %entry
+; CHECKBE-NEXT:    vrev64.16 q1, q0
+; CHECKBE-NEXT:    vmovnt.i32 q1, q1
+; CHECKBE-NEXT:    vrev64.16 q0, q1
+; CHECKBE-NEXT:    bx lr
+entry:
+  %c1 = call <4 x i32> @llvm.arm.mve.vreinterpretq.v4i32.v8i16(<8 x i16> undef)
+  %c2 = call <4 x i32> @llvm.arm.mve.vreinterpretq.v4i32.v8i16(<8 x i16> %a)
+  %strided.vec = shufflevector <4 x i32> %c1, <4 x i32> %c2, <8 x i32> <i32 0, i32 4, i32 1, i32 5, i32 2, i32 6, i32 3, i32 7>
+  %out = trunc <8 x i32> %strided.vec to <8 x i16>
+  ret <8 x i16> %out
+}
+
+define arm_aapcs_vfpcc <8 x i16> @vmovn16b_undef2(<16 x i8> %a) {
+; CHECK-LABEL: vmovn16b_undef2:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    bx lr
+;
+; CHECKBE-LABEL: vmovn16b_undef2:
+; CHECKBE:       @ %bb.0: @ %entry
+; CHECKBE-NEXT:    vrev64.8 q1, q0
+; CHECKBE-NEXT:    vrev64.16 q0, q1
+; CHECKBE-NEXT:    bx lr
+entry:
+  %c1 = call <8 x i16> @llvm.arm.mve.vreinterpretq.v8i16.v16i8(<16 x i8> %a)
+  %c2 = call <8 x i16> @llvm.arm.mve.vreinterpretq.v8i16.v16i8(<16 x i8> undef)
+  %out = shufflevector <8 x i16> %c1, <8 x i16> %c2, <8 x i32> <i32 0, i32 9, i32 2, i32 11, i32 4, i32 13, i32 6, i32 15>
+  ret <8 x i16> %out
+}
+
+define arm_aapcs_vfpcc <8 x i16> @vmovn16b_undef1(<16 x i8> %a) {
+; CHECK-LABEL: vmovn16b_undef1:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    bx lr
+;
+; CHECKBE-LABEL: vmovn16b_undef1:
+; CHECKBE:       @ %bb.0: @ %entry
+; CHECKBE-NEXT:    vrev64.8 q1, q0
+; CHECKBE-NEXT:    vrev64.16 q0, q1
+; CHECKBE-NEXT:    bx lr
+entry:
+  %c1 = call <8 x i16> @llvm.arm.mve.vreinterpretq.v8i16.v16i8(<16 x i8> undef)
+  %c2 = call <8 x i16> @llvm.arm.mve.vreinterpretq.v8i16.v16i8(<16 x i8> %a)
+  %out = shufflevector <8 x i16> %c1, <8 x i16> %c2, <8 x i32> <i32 0, i32 9, i32 2, i32 11, i32 4, i32 13, i32 6, i32 15>
+  ret <8 x i16> %out
+}
+
+define arm_aapcs_vfpcc <8 x i16> @vmovn32_badlanes(<4 x i32> %src1) {
+; CHECK-LABEL: vmovn32_badlanes:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    vmov r0, s0
+; CHECK-NEXT:    vmov.16 q1[1], r0
+; CHECK-NEXT:    vmov r0, s1
+; CHECK-NEXT:    vmov.16 q1[3], r0
+; CHECK-NEXT:    vmov.16 q1[5], r0
+; CHECK-NEXT:    vmov r0, s2
+; CHECK-NEXT:    vmov.16 q1[7], r0
+; CHECK-NEXT:    vmov q0, q1
+; CHECK-NEXT:    bx lr
+;
+; CHECKBE-LABEL: vmovn32_badlanes:
+; CHECKBE:       @ %bb.0: @ %entry
+; CHECKBE-NEXT:    vrev64.32 q1, q0
+; CHECKBE-NEXT:    vmov r0, s4
+; CHECKBE-NEXT:    vmov.16 q2[1], r0
+; CHECKBE-NEXT:    vmov r0, s5
+; CHECKBE-NEXT:    vmov.16 q2[3], r0
+; CHECKBE-NEXT:    vmov.16 q2[5], r0
+; CHECKBE-NEXT:    vmov r0, s6
+; CHECKBE-NEXT:    vmov.16 q2[7], r0
+; CHECKBE-NEXT:    vrev64.16 q0, q2
+; CHECKBE-NEXT:    bx lr
+entry:
+  %strided.vec = shufflevector <4 x i32> %src1, <4 x i32> undef, <8 x i32> <i32 4, i32 0, i32 5, i32 1, i32 6, i32 1, i32 7, i32 2>
+  %out = trunc <8 x i32> %strided.vec to <8 x i16>
+  ret <8 x i16> %out
+}
+
+define arm_aapcs_vfpcc <16 x i8> @vmovn16trunct_undef2(<16 x i8> %a) {
+; CHECK-LABEL: vmovn16trunct_undef2:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    bx lr
+;
+; CHECKBE-LABEL: vmovn16trunct_undef2:
+; CHECKBE:       @ %bb.0: @ %entry
+; CHECKBE-NEXT:    bx lr
+entry:
+  %c1 = call <8 x i16> @llvm.arm.mve.vreinterpretq.v8i16.v16i8(<16 x i8> %a)
+  %c2 = call <8 x i16> @llvm.arm.mve.vreinterpretq.v8i16.v16i8(<16 x i8> undef)
+  %strided.vec = shufflevector <8 x i16> %c1, <8 x i16> %c2, <16 x i32> <i32 0, i32 8, i32 1, i32 9, i32 2, i32 10, i32 3, i32 11, i32 4, i32 12, i32 5, i32 13, i32 6, i32 14, i32 7, i32 15>
+  %out = trunc <16 x i16> %strided.vec to <16 x i8>
+  ret <16 x i8> %out
+}
+
+define arm_aapcs_vfpcc <16 x i8> @vmovn16trunct_undef1(<16 x i8> %a) {
+; CHECK-LABEL: vmovn16trunct_undef1:
+; CHECK:       @ %bb.0: @ %entry
+; CHECK-NEXT:    vmovnt.i16 q0, q0
+; CHECK-NEXT:    bx lr
+;
+; CHECKBE-LABEL: vmovn16trunct_undef1:
+; CHECKBE:       @ %bb.0: @ %entry
+; CHECKBE-NEXT:    vrev64.8 q1, q0
+; CHECKBE-NEXT:    vmovnt.i16 q1, q1
+; CHECKBE-NEXT:    vrev64.8 q0, q1
+; CHECKBE-NEXT:    bx lr
+entry:
+  %c1 = call <8 x i16> @llvm.arm.mve.vreinterpretq.v8i16.v16i8(<16 x i8> undef)
+  %c2 = call <8 x i16> @llvm.arm.mve.vreinterpretq.v8i16.v16i8(<16 x i8> %a)
+  %strided.vec = shufflevector <8 x i16> %c1, <8 x i16> %c2, <16 x i32> <i32 0, i32 8, i32 1, i32 9, i32 2, i32 10, i32 3, i32 11, i32 4, i32 12, i32 5, i32 13, i32 6, i32 14, i32 7, i32 15>
+  %out = trunc <16 x i16> %strided.vec to <16 x i8>
+  ret <16 x i8> %out
+}
+
+declare <4 x i32> @llvm.arm.mve.vreinterpretq.v4i32.v8i16(<8 x i16>)
+declare <8 x i16> @llvm.arm.mve.vreinterpretq.v8i16.v16i8(<16 x i8>)